This whole thing was emphatically partisan from the get-go. Is it any wonder McConnell is willing to reject it out of hand?
The House are simply the overzealous prosecutors bringing charges... they only need probable cause for them as grand jurors to indict.
The Senate is where there is the allegedly fair trial, where the burden of proof and evidence and testimony, has to be BEYOND a reasonable doubt for Senators/ the jury to convict and 2/3s having to do such for eviction from office.
This is why all evidence is not needed to Charge
and More Evidence....as much as possible, from both the defendant and prosecution, so the jury can make, impartial, sound, decisions.